Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered; the description adds real context by noting the result is a 'full current' inventory that maps games to existing catalogue and price-guide files. It doesn't warn about response size or whether the inventory is cached/snapshot, which is the only remaining gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, no filler: the first defines the return, the second defines the intended use. The return contract is front-loaded before the usage advice.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

A parameterless discovery tool with an output schema, read-only annotations, and a description covering both what comes back and why you'd call it. Nothing an agent needs in order to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly implies the call is unfiltered and returns everything.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Returns the full current Cardmarket S3 game-ID inventory') and adds the secondary payload (which catalogue and price-guide files exist per game). This clearly separates it from siblings like cardmarket_catalog and cardmarket_price_guide, which operate on a game already chosen.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly prescribes the workflow: 'Use it to discover a valid game_id before requesting game-specific data.' That is a clear when-to-use and prerequisite rule, but it never names the sibling tools it feeds (cardmarket_catalog, cardmarket_price_guide) or states any when-not condition.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.